The present invention relates generally to equipment for processing semiconductor wafers. More particularly, the present invention relates to a polishing belt and associated linear polisher for chemical mechanical polishing of semiconductor wafers.
Chemical mechanical polishing (CMP) is used for planarizing semiconductor wafers during processing of the wafers. Because semiconductor circuits on wafers are commonly constructed in layers, where a portion of a circuit is created on a first layer and conductive vias connect it to a portion of the circuit on the next layer, each layer can add or create topography on the wafer that must be smoothed out before generating the next layer. In order to improve the manufacturability of the circuits on the wafer, many processing steps require planarizing the wafer surface. For example, to improve the uniformity of deposition of the conductive vias, the wafer is planarized prior to deposition to reduce the peaks and valleys on the surface over which the metal is deposited.
In conventional planarization technology, a semiconductor wafer is supported face down against a moving polishing pad. Two types of polishing or planarizing apparatus are commonly used. In rotary planarizing technology, a wafer is secured on a chuck and is brought into contact with the polishing surface. A flat polishing pad mounted on a rotating table forms the polishing surface. In linear planarizing technology, an endless belt travels over two or more rollers. The wafer is placed against the moving polishing surface of the belt. An example of a linear polishing system is the Teres(trademark) CMP System manufactured by Lam Research Corporation, Fremont, Calif.
A key component of a linear CMP system is the polishing belt assembly. Conventionally, the belt assembly includes a supporting band made of stiff material such as stainless steel. Polishing pads are attached to the stainless steel to form the polishing surface. In some cases, the pads have two layers, for example, a soft cushion layer and a polishing layer. The stainless steel band forms a strong, reliable support for the polishing pads.
The polishing pad needs to be attached with the supporting band so that it does not slip out of place, or deform due to excessive stretching and wear and become loosely attached with the support band. With conventional CMP systems, the polishing pad is attached to the supporting band with an adhesive such as a pressure sensitive adhesive. However, the pads typically have a finite lifetime, for example, 500 wafers. When the pads become worn, they must be removed and replaced. Using an adhesive may necessitate a longer change out time for a replacement polishing pad, because the xe2x80x9coldxe2x80x9dadhesive will have to be removed from the supporting band before a new polishing pad can be attached to the supporting band.
Furthermore, adhesives may wear and lose their adhering qualities, causing the polishing pad to slip out of position. Alternatively, the polishing pad may stretch an excessive amount and deform, resulting in a polishing pad that is loosely attached to the support band. Either alternative may lead to wafers being improperly polished.
Accordingly, there is a need in the art for an improved polishing belt assembly for CMP systems.
A method for producing a chemical mechanical planarization polishing belt structure is provided herein. According to a first aspect of the method, a strip of substantially rigid material is formed into a support belt having an interior surface and an exterior surface. At least a portion of the exterior surface of the support belt is altered to form a plurality of gripping members integral with the exterior surface of the support belt. Finally, an interior surface of a seamless CMP belt is applied to the exterior surface of the support belt, with the plurality of gripping members engaging the interior surface of the seamless CMP belt in a non-slip grip.
According to another aspect of the method, a plurality of gripping members is attached to at least a portion of the exterior surface of the support belt.
A chemical mechanical planarization polishing belt structure is also provided herein. A first aspect of the belt structure includes an inner support belt constructed of a rigid material having an outer surface. The outer surface of the inner support belt comprises a plurality of mechanical grips integrally formed from displaced support belt material. An outer belt having an inner surface mechanically engages with the mechanical grips of the inner support belt. The outer belt also includes an outer surface that comprises a seamless CMP polishing pad. The outer diameter of the inner support belt is larger than the inner diameter of the outer belt.
In another embodiment, the outer surface of the inner support belt includes a plurality of mechanical grips attached to the outer surface of the inner support belt.